The present invention relates to an apparatus for stacking a stream of printed materials in signature form. Stackers are commonly employed in the printing industry for collecting and aligning sheets of paper such as those produced by a printing press, cutter and folder arrangement. In the conventional arrangement, a stream of sheets, for example in the form of newspapers, is collected on a conveyor which receives the sheets from the printing press, cutter or folder and which moves the sheets to the stacker. The stacker receives the sheets in serial form from the conveyor and forms a neat aligned stack which is easy to tie together for removal and transportation.
Many stacking arrangements are known in the art. U.S. Pat. No. 2,933,314 describes one apparatus for stacking flexible sheets by collecting them down an inclined conveyor. This arrangement is complex and very expensive. U.S. Pat. No. 4,361,318 provides an improvement system wherein a stream of horizontal signatures is provided to a first stacker conveyor. This first conveyor compresses the signatures between opposing belts and moves the stream around a drum to change its direction vertically. The stream is then deposited on a second conveyor which moves horizontally. This provides a horizontally growing, aligned stack of sheets which is relatively easy to handle as desired. A key problem with this machine is that the drum can only be of limited size for practical use within a stacking machine. Typically, such drums are approximately one foot in diameter. This means that the incoming signatures must be bent around a relatively small drum radius of approximately six inches. This bending of signatures around a small drum radius tends to break the backbone of thicker signatures such as those in the form of books. This is particularly true since overlapping books in shingled stream form travel in plies two or three times the thickness of a single book. This prior art device also causes skewing of shingled signatures, due to the single drum acting with an outer belt to transfer the signatures from a first direction and position to a stacking receiver for bundling. These devices have also required continual adjustment of the outer belt, resulting in frequent damage to and jamming of signatures and the need to remove jammed signatures. The removal of skewed and jammed signatures requires a production stoppage and added production costs. This drum is also a problem with the machine described in U.S. Pat. No. 2,933,314.
In an attempt to overcome this drum disadvantage, U.S. Pat. No. 4,463,940, which is incorporated herein by reference, uses an upswept arcuate array of rollers in place of a single drum. This provides a greatly increased effective travel radius which treats the signatures much more gently. This latter stacking apparatus has a reduced tendency to skew and jam signatures by sequentially engaging signatures with crusher rollers and opposed endless timing belts which are compression mounted by the series of rollers. The series of rollers, as distinct from a single drum roller, distributes the applied compression more evenly along the overlapped signatures, providing constant compression. There is also greater control over the rapidly moving, highly compressed signatures, resulting in a more economical stacking since fewer signatures are lost through jamming and the conveyor belts can move at substantially constant speed.
However, even this latter stacking apparatus has disadvantageous. Since the endless timing belts which follow the path of the rollers are driven under tension, they have a tendency to break. It has always been a problem to replace broken endless timing belts since all of the rollers must be removed in an operation lasting several hours. Not only is such an operation labor intensive, but the stacker is out of production for this entire time. In state of the art stackers, each of the ends of the compression rollers are mounted for rotation through bearing bores in the machine's frame. Therefore, both ends of each roller must be disengaged and pulled through and away from the frame in order to install a new endless timing belt around every roller end. This includes both drive shaft pulley assemblies and idler rollers. The present invention improves on this arrangement by providing quick release mountings for the rollers and drive shaft pulley assemblies. By this means, broken belts can be quickly replaced, thus reducing labor costs and equipment down time. By the present invention, the shafts of drive shaft pulley assemblies, that is pulley assemblies which are spun by the machine's motor via drive belts and sprockets, are mounted by a two bolt flanged bearing with a screw clamp collar. These allow shafts to be quickly released and moved to provide a small space between the shaft and stacker frame which is sufficient to allow belt replacement through this space. The idler rollers in the upswept arcuate array of rollers which replaced the single drum, are mounted in a frame within a frame construction. The rollers are gang mounted for rotation within an inner frame. The inner frame is then fixed to the main frame of the machine by a quick release mounting. Therefore, when a timing belt breaks, an operator need not loosen the individual arcuate rollers at all. Rather, the inner frame is freed from the outer frame and the belt is wound around the inner frame into position on the rollers. Then the inner frame is re-set. Not only is labor and machine downtime reduced, but also, the life of the rollers is extended since frequent roller unmounting and mounting erodes the roller shaft ends. Various mountings for conveyor rollers are shown in U.S. Pat. Nos. 5,004,223; 4,984,677; 4,513,859; 4,146,126; 3,743,078; 3,664,488; 3,122,945 and 2,998,731.
These and other features and advantages and improvements will be in part discussed and in part apparent to one skilled in the art upon a consideration of the detailed description of the preferred embodiment and the accompanying drawings.